Although the visually impaired normally become very adept at moving around known environments, including outdoors, difficulties arise when the person is in an unfamiliar environment. The reason for this is that there is much environmental information which can only be discerned visually and which gives little or no information via other senses such as hearing or smell. Although this information can to a certain extent be learned for a familiar environment, it is of no assistance in an unfamiliar environment.
A system being developed to provide navigation for the visually impaired includes a satellite Global Positioning System (GPS) and a digital map specially adapted for visually impaired users. The system includes a first receiver for receiving a signal for the known GPS satellites, a second receiver for receiving a differential GPS (DGPS) correction signal from a fixed base station; a computer for calculating the user's position, for correlating this position with the digital map and for determining environmental obstacles and directions for the user; and a user interface, typically a voice synthesizer.
The GPS satellite system only provides a Standard Positioning resolution of around 100 meters. The differential correction signal is thus provided to increase resolution to around 1 to 5 meters.
With this system, the user must carry all the above components, which can be onerous.